Treatment of material for hysteresis application



United States Patent 3,301,720 TREATMENT OF MATERIAL FOR HYSTERESIS APPLICATION Andrew J. Griest, Jr., Pittsburgh, Pa., assignor to Allegheny Ludlum Steel Corporation, Brackenridge, Pa., a corporation of Pennsylvania No Drawing. Filed Jan. 29, 1964, Ser. No. 341,125

8 Claims. (Cl. 148-120) This invention relates to ferrous base alloys, and more particularly to material which is suitable for use as rotors on hysteresis motors and the like.

Materials which are desirable for r-otors of hysteresis motors, generally referred to as hysteresis materials, are characterized by having high hysteresis efficiency ,and superior hysteresis loss at relatively low magnetizing fields. (Hysteresis loss is measured in units of energy per unit volume. Some commonly used units are gaussoersteds, joules per cubic centimeter, or joules per cubic inch; hysteresis efliciency is defined as the hysteresis loss per cycle divided .by the peak magnetizing force.) There are several excellent, prior art hysteresis materials, but most of them require a final high temperature heat treatment after they are formed into rotors or rotor parts'to develop their hysteresis properties. This heat treatment cannot be performed before the parts are formed, since this heat treatment also increases the hardness .of the material, thus making it difiicult or impossible to stamp or form successfully. These heat treatments are critical, if reproducible properties are to be obtained, and are therefore expensive; also, thecost ofscrapping a part is high if the heat treatment is improperly performed, since finished or semi-finished parts are involved. Additionally, many of the prior art hysteresis materials contain uppreciable amounts of carbon as an essential element, thus rendering the material subject'to decarbonization during heat treatment, which will reduce the hysteresis characteristics obtained. Further, some prior art materials are subject to a change in hysteresis properties at even slightly elevated temperatures normally encountered in the operation of hysteresis motors.

It is therefore a principal object of this invention to provide a ferrous base alloy which, when properly treated,

' will have outstanding hysteresis characteristics.

Yet an additional object of this invention is the provision of a method of processing an, iron-manganese alloy to provide outstanding hysteresis characteristics.

Still afurther, more particular object of this invention is the provision of a hysteresis material which does not require high temperature heat treatment after forming to develop hysteresis properties.

Still another object of this invention is the provision of 3,301,720 Patented Jan. 31, 1967 ICC a substantially carbon-free alloy and method of processing which will yield outstanding hysteresis characteristics.

Yet a further object of this invention is the provision of a hysteresis material which, when processed, will exhibit little change in characteristics at normal motor operating temperatures.

These and other objects, together with a fuller understanding of the invention, will become apparent from the following description when taken in conjunction with the appended claims.

In iron base alloys, a metallographic structure which is a mixture of ferrite and austenite with a substantial amount of, and preferably at least about 50%, ferrite provides excellent hysteresis properties. I have found that an alloy consisting essentially of a mixture of iron and from about 7% to about 15% manganese will produce excellent material for hysteresis applications if the alloy is properly warm worked. In this warm working operation the material must be reduced in cross sectional area at least 99% while the material is maintained in the temperature range of from about 800 F. to about 950 F. When an :alloy Within the above composition range is warm worked in this temperature range, the mechanical working will produce a metallographic structure which is a mixture of austenite and ferrite, and the austenite will be retained upon cooling to ambient temperature. For a given temperature of warm working, the lower the manganese content the higher the percentage of ferrite that will be formed, and for a given manganese content, the higher temperature at which warm working takes place the lower the percentage of ferrite that will he formed. -At the lower percentages of manganese and lower working temperatures, at least ferrite will be formed. At higher working temperatures and/or higher percentages of manganese, there is a greater percentage of austenite formed and retained, although there is still an appreciable amount of ferrite present, probably as particles or as platelets dispersed in the austenite matrix.

The properties of the material may be developed by any suitable method of working such as by rolling, swaging, drawing or extruding, but regardless of the form of working chosen, the material must be reduced in cross sectional area at least 99% in the temperature range of from 800 F. to 950 F.

Table I below shows the magnetic properties of various compositions of warm worked material. The specimens were produced by warm rolling a slab of each material to the final thickness indicated. The rolling was done in several passes, with the material being heated to between 850 F. and 950 F. for the rolling, and with reheating being done as required to maintain the material in this temperature range. The total reduction in area in each case was between 99.1% and 99.6%.

TABLE I.-MAGNETIO PROPERTY DATA Nominal Peak Hysteresis Hysteresis Maximum Residual Coercive Normal Composition Magnetizing Loss per Efiiciency Flux Induction Force Permea- Spec. No. Force Cycle, Eh Joules, Oer- Density Br 11;. bllity (Oersteds) 10 g.-oe. sted-cm. m (Gauss) (Oersteds) B /H p Mn Fe 1 Hp Eh Ell/Hp (Gauss) 7. 3 Bal. 30 0.51 0.136 8, 500 6, 620 18. 0 283 HMR 23 (0 015 'Rmg) 40 1.05 0.208 12,680 11,000 24.0 317 50 1. 20 0. 191 13,600 12, 000 25. 0 272 7.3 Bal. 30 0.57 0.150 8, 750 7,250 19.0 291 HMR 24 (0 015 Rmg) 40 1.04 O. 206 12,560 10,750 24. 0 314 50 1. 22 0. 194 13,620 12, 000 24. 5 272 4 Bal. 30 0.45 0.120 8,190 6, 370 16.0 273 HMR 25 (0.016 Rmg) 8 40 0.87 0.172 11,750 9, 750 21. 0 294 50 1. 06 0.169 13, 250 11, 125 22. 0 205 TABLE L-MAGNETIO PROPERTY DATA-Continued Nominal Peak Hysteresis Hysteresis Maximum Residual Coercive Normal Composition Magnetizing Loss per Efficiency Flux Induction Force Permea- Spee. No. Force Cycle, Eh Joules, Oer- Density B H, bility (Oersteds) 10 g.-oe sted-om. m (Gauss) (oersteds) Bm/H r Mn Fe 1 H, E h Eh/H (Gauss) HMR-26 (0.015" Ring) 8. 4 Bal. 30 0. 495 0. 131 8,750 6,870 17. 291 40 0. 895 0. 177 12,370 10, 250 21. 0 309 50 1. 06 0. 169 13, 500 11, 350 21. 270 70 1. 18 0. 134 14, 620 12, 500 22. 0 209 80 1. 22 0. 121 15, 000 12, 500 23. 0 187 TIME-27 (0.015" Ring) 10. 0 Bal. 40 0. 576 0. 114 7, 750 6, 000 20. 0 193 50 0. 972 0. 155 10, 430 8, 430 26. 5 208 60 1. 16 0. 155 11, 560 9, 680 29. 5 193 70 1. 28 0. 145 12, 190 10, 375 30. 0 174 90 1. 44 0. 127 12, 990 10, 940 30. 2 144 100 1. 47 0.117 13,190 180 30. 5 132 HMR-28 (0.015 Ring) 10. 0 139.1. 40 0.558 0.111 7,750 5,870 22. 0 193 50 0. 947 0. 151 10, 370 8,370 27. 0 207 60 1. 19 0. 157 11,620 9, 620 29. 0 194 70 1. 30 0. 147 12, 200 10, 370 31. 0 174 90 1. 41 0. 125 13, 000 11, 000 30. 0 144 100 1. 48 0. 117 13,200 11, 000 31. 0 132 HMR-29 (0.015 Ring) 12. 2 Bal. 60 0. 192 0. 025 2, 750 1, 190 26. 0 45. 5 70 0. 382 0. 043 3,750 2, 500 34. 0 53. 5 80 0. 63 0. 062 4, 870 3, 250 43. 0 61. 0 100 1. 0. 087 6, 500 4, 930 51. 0 65. 0

HMR- (0.015 Ring) 12. 4 Bal. 60 0.189 0.025 2, 750 1, 250 23. 0 46. 0 70 0. 372 0. 042 3,810 2, 250 33. 5 54. 5 80 0. 688 0. 068 5, 090 3, 430 42. 0 62. 6 100 1. 08 0. 085 6, 620 4, 930 50. 0 66. 2

HMR-31-32 (0.025 Strip in R.D.). 7. 3 Bal. 30 0. 78 0.208 8,620 7,870 25. 5 287 1. 49 0. 298 14, 370 13, 600 27. 5 371 50 1. 61 0. 255 14, 750 14, 000 28. 0 294 70 1. 66 0. 188 15,250 14, 250 23. 5 218 80 1. 68 0. 167 15, 500 14, 250 28. 5 193 HM R-33-34 2 8. 4 Bal. 30 0. 86 0. 228 10, 000 9, 000 23. 5 333 40 1. 35 0. 268 13,750 13, 000 26. 0 343 50 1. 46 0. 232 14,370 13, 370 26. 5 287 70 1. 53 0. 174 14, 870 14, 000 27. 0 212 80 1. 0. 154 15, 120 13,870 27. 0 189 HMR-35-36 (0.025 Strip) 10. 0 Bal. 40 1. O1 0. 200 8, 500 7, 750 32. 0 212 50 1. 65 0. 262 12, 250 11, 500 35. 5 245 1. 81 0. 240 13, 120 12,370 36. 5 218 70 1. 89 0. 233 13,370 12,500 37. 0 191 90 1. 98 0. 175 13,750 12,870 37. 5 152 100 2. 00 0. 159 14, 000 12,870 37. 5 140 HMR-37-38 (0.025 Strip) 12. 2 Bal. 50 0. 076 0. 0121 1, 120 500 23. 0 22 60 0. 349 0. 046 2,750 1, 750 44. 0 45 70 0. 941 0. 107 5, 120 4, 370 55. 0 73 80 1. 45 0. 144 6, 750 6, 000 58. 5 84 100 2. 02 0. 161 8, 620 7, 870 63. 0 86 HMR-40 (0.015" Strip). 12.2 Bal. 70 0.326 0. 037 2,500 1,500 45.0 36 80 0. 860 0. 086 4, 620 3, 500 58. 0 58 100 2. 03 0. 161 8, 120 7,250 70. 0 81 120 2. 0. 176 9, 620 8, 620 75. 0 80 180 3. 21 0. 142 10,870 9, 620 78. 0 60 HF-41 (0.015 Strip in R.D.) 15. 2 Bal. 50 0.017 4 HMR-39 (0.015" Strip in R.D.). 8. 4 Bal. 30 0.158 0. 042 112 40 1. 01 0. 200 259 50 1. 46 0. 232 262 1. 0. 197 209 1. 77 0. 176 189 2 Average value of two tests in the direction of rolling.

It can be seen from an examination of Table I that 60 sharply when the alloy contains more than 15% maneach of the samples, except the 15.2% manganese specimen, possesses excellent hysteresis properties, particularly as measured in the rolling direction, although the ring tests, which gave a somewhat lower value, also show very good hysteresis properties. The alloy containing 7.3% manganese attains a peak efficiency at a very low magnetizing force, usually about 30 to 40 oersteds, whereas the alloy containing 10% manganese reaches peak efficiency at about 50 to 60 oersteds and the 12.2% manganese specimens do not reach their peak efiiciency until greater than oersteds. increased beyond about 15%, as in the 15.2% manganese sample, this peak magnetizing force becomes prohibitively high for hysteresis applications, and also the induction As the manganese content is ganese. Hence, the maximum permissible manganese content is about 15%. If the alloy contains less than about 7% manganese, its warm workability is impaired and the alloy tends to crack before full reduction can be achieved; hence the minimum manganese value is 7%. An alloy containing in the neighborhood of about 12% manganese is the most desirable for hysteresis applications because of its combination of relatively high hysteresis loss and hysteresis efliciency at reasonably low peak magnetizing forces.

The warm Working temperature, in order to produce the desired properties, must be at least 800 F. or the hysteresis loss and the actual value of the hysteresis eificiency are too low for the material to be useful as a values and the value of the hysteresis efficiency fall 06? 75 hysteresis material. On the other hand, if the warm working temperature exceeds about 950 F., there is a change in the metallurgical structure which results in a decrease in the coercive force and also a decrease in the residual induction, thus making the material unsuitable for hysteresis applications. The exact reason for such metallurgical change is not completely understood; however, it is believed it is due at least in part to a tendency toward particle coarsening, or growth of the ferrite particles or platelets immediately after working which, in effect, counteracts the effect of the mechanical working by returning the particles to the same size as they were previous to working. Whatever the reason, however, the material cannot be warm worked above about 950 F. and provide suitable material for hysteresis application. Also, to develop suitable hysteresis properties, the material must be warm reduced at least 99% in thickness, and preferably about 99.6% to about 99.8%, since the maximum hysteresis loss and maximum coercive force of the material increases as the percent reduction is increased to about 99.8%, but both drop ofi rather sharply with reductions greater than 99.8%.

Although the primary constituents of the alloy of this invention are iron and manganese, it is to be understood th'atthere will normally be present other elements as residual impurities such as carbon, silicon, sulfur and phosphorus; however, these and other normal impurities, when present only in residual amounts, will not affect the basic properties of the alloy to any appreciable extent.

An alloy processed according to this invention has its hysteresis properties fully developed in the as-processed condition and does not require any high temperature heat treatment to develop these properties after the material is formed into rotors. The material in the as-processed condition is soft and ductile enough to be formed by stamping or other operations.

Although several embodiments of this invention have been shown and described, various adaptations and modifications may be made without departing from the scope and appended claims.

I claim:

1. A method of producing a material suitable for rotors in hysteresis motors comprising the steps of, producing 6 a material having from about 7.0% to about 15% manganese, the balance essentially iron and residual impurities, and reducing said material at least 99% in cross sectional area, said reduction in area being carried out with the material between about 800 F. and 950 F.

2. The methodof claim 1 wherein the reduction in cross sectional area is effected by rolling in successive passes.

3. A method of producing a material suitable for rotors in hysteresis motors comprising the steps of, producing a material having from about 7% to about 15% manganese, the balance essentially iron and residual impurities, and reducing said material at least 99% and not more than 99.8% in cross sectional area, said reduction in area being carried out with the material between about 800 F. and 950 F.

4. The method of claim 3 wherein the material is reduced at least 99.6% in cross sectional area.

5. A material suitable for rotors in hysteresis motors comprising, from about 7% to about 15% manganese, the remainder essentially iron and residual impurities, said material having been reduced in cross sectional area at least 99% at temperatures between about 800 F. and 950 F said material being characterized by a relatively high hysteresis efliciency and hysteresis loss at relatively low peak magnetizing fields.

6. The material of claim 5 and in which said reduction of cross sectional area is at least 99.6%.

7. The method of claim 1 wherein the material produced thereby is further subjected to a physical forming operation without further high temperature heat treatment to produce a rotor part therefrom.

8. The method of claim 7 wherein the forming operation is a stamping operation.

References Cited by the Examiner UNITED STATES PATENTS 2,569,468 10/1951 Gaugler 148-120 DAVID L. RECK, Primary Examiner.

N. F. MARKVA, Assistant Examiner. 

1. A METHOD OF PRODUCING A MATERIAL SUITABLE FOR ROTORS IN HYSTERESIS MOTORS COMPRISING THE STEPS OF, PRODUCING A MATERIAL HAVING FROM ABOUT 7.0% TO ABOUT 15% MANGANESE, THE BALANCE ESSENTIALLY IRON AND RESIDUAL IMPURITIES, AND REDUCING SAID MATERIAL AT LEAST 99% IN CROSS SECTIONAL AREA, SAID REDUCTION IN AREA BEING CARRIED OUT WITH THE MATERIAL BETWEEN ABOUT 800*F. AND 950*F. 